Cathode ray deflecting yoke



March 1941. A. v. BEDFORD ETAL 2.234.038

CATHODE RAY DEFLECTING YOKE Filed June 50, 19159 Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE CATHODE RAY DEFLECTING YOKE Application June 30, 1939, Serial No. 282,304

1 Claim.

Our invention relates to electromagnetic deflecting devices for cathode ray tubes and particularly to such devices which are to be used with cathode ray picture transmitter tubes such as Iconoscopes of the like.

It has been found that picture transmitter or pick-up tubes of the above-mentioned type are specially susceptible to stray electromagnetic or electrostatic fields. For this reason, if electromagnetic deflection is employed, the deflecting yoke must be carefully shielded or there will be disturbances in the transmitted picture caused by the deflecting field. 1 It is, accordingly, an object of our invention to provide an improved cathode ray deflecting yoke designed to keep stray electrostatic and electromagnetic fields at a minimum value.

It is a further object of our invention to provide an improved electromagnetic deflecting yoke which is compact in design and economical to manufacture.

In the preferred embodiment of our invention, the basic design of the deflecting yoke is the same as that described in Tolson and Malofi Patent 2,155,514, issued April 25, 1939, the deflecting coils being distributed windings which are positioned in slots in an iron core. In accordance with our invention, the deflecting coils are substantially completely surrounded by shielding means comprising annular shaped end shields of brass or the like and a cylindrical screen located inside the deflecting yoke and adjacent tothe cathode ray tube.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Figure l is a view in longitudinal section of a deflecting yoke embodying the invention, the i0 yoke being shown as applied to a cathode ray tube,

Figure 2 is a view taken on the line 2--2 of F 1', and

Figure 3 shows the type of shielding screen employed in the yoke of Fig. 1.

Referring to Fig. 1, our deflecting yoke is shown applied to a picture pick-up tube such as an Iconoscope indicated at I0. The deflecting yoke comprises an iron core ll having a plurality of to radial slots I 2 therein as illustrated in Fig. 2.

In the slots l2 there is located a pair of oppositely disposed horizontal deflecting coils and at right angles to these coils there is located a pair of vertical deflecting coils as described in the said Tolson and Malofi patent. The ends of these deflecting coils are shown at 13 and I4 in Fig. 1. Shielded output leads for the horizontal and vertical deflecting coils are indicated at l8 and I1, respectively.

The above-described deflecting yoke structure differs from that described in the Tolson and Malofl patent in that the laminations making up the iron core II are held together by means of a cylinder I8 of brass or the like which has its ends spun over as indicated to clamp the laminations firmly between the spun ends. Suitable insulating material l9, such as sheets of fiber, is placed between the core II and the cylinder it before the cylinder ends are spun over. F

In accordance with our invention, the deflecting windings are electrostatically shielded from the cathode ray tube l0 by means of annular end members 2| and 22 which fit over the ends of the deflecting yoke, and by means of a cylindrical shielding screen 23. 0

Each of the shielding end members 2| and 22 is of brass or some other material having good electrical conductivity and is so shaped as to have a sliding fit on the brass sleeve Hi to frictionally engage it. Also, the end shielding members are so shaped as to cover the ends of the deflecting coil windings I3 and M.

The shielding screen 23 is made, as illustrated in Fig. 3, by weaving conducting threads or wires with threads of insulating material, the wires running longitudinally of the cathode ray tube axis. In the example of Fig. 3, the warp of the screen is cotton thread, while the woof is double cotton covered copper wire. 0

As indicated in Fig. l, the right hand end of the screen 23 is soldered or otherwise electrically connected to the shielding member 2|. The other end of the screen is not connected to anything whereby the presence of closed electrical paths in the screen 23 is avoided.

In order to prevent the left-hand end of the screen 23 from coming into contact with the shielding member 22 and in order to avoid shortcircuiting of the deflecting coil ends, there is provided an annular insulating member 26 of fiber, paper or the like. Another annular insulating member 21 is provided inside the shielding member 2| to prevent short-cirouiting of the other deflecting coil ends.

It will be seen that the shielding members 2| and 22 and the screen 23 form a toroidal shielding structure which completely surrounds the deflecting coil windings.

When the deflecting yoke is in use in a circuit,

the above described shielding as Well as the iron core H is grounded. In practice, the ground connection is usually through the shield covering of the deflecting coil leads I5 and I1, this shield covering being grounded and also being connected to the shield member 2|.

From the foregoing, it will be apparent that the deflecting coils are completely surrounded by electrostatic shielding means whereby the electrostatic field produced during deflection does not affect the cathode ray tube operation. Also, there is a negligible amount of stray magnetic flux because of the iron core II.

We claim as our invention:

A deflecting yoke comprising a magnetic core substantially cylindrical in shape and having radial slots therein extending from the inner surface of the core, a pair of oppositely disposed distributed windings located in said slots with their ends extending beyond said core, an annular shielding member attached to one end of said core and surrounding the ends of the windings which extend beyond said core end, a second annular shielding member attached to the other end of said core and surrounding the ends of the windings which extend beyond said other end of the core, and a cylindrical screen positioned inside said core, said screen comprising wires running longitudinally of said yoke and connected together electrically at one end only and further comprising insulating threads running transversely of said wires.

ALDA V. BEDFORD.

FELIX E. CONE. 

